Over a third of global fish stocks are being harvested at unsustainable levels – just one example of how human activity is harming oceans, which cover more than 70 per cent of the Earth’s surface.

UN Secretary-General António Guterres has called for greater action to protect oceans in his message to mark World Oceans Day on Thursday.

“The ocean is the foundation of life. It supplies the air we breathe and food we eat. It regulates our climate and weather. The ocean is our planet’s greatest reservoir of biodiversity,” he said.

Besides these benefits, the ocean also produces resources that sustain communities, prosperity and health.  Worldwide, more than a billion people alone rely on fish as their main source of protein.

“We should be the ocean’s best friend. But right now, humanity is its worst enemy,” he said, pointing to the evidence.

The UN chief said human-induced climate change is heating the planet, disrupting weather patterns and ocean currents, and altering marine ecosystems and the species living there.

Marine biodiversity is also under attack from overfishing, over-exploitation and ocean acidification, fish stocks are being depleted, and coastal waters have been polluted with chemicals, plastics and human wastes.